The invention relates to a method for adjusting the axle geometry of a vehicle and to an adjusting device that adjusts the axle geometry of a vehicle. Furthermore, the invention relates to an assembly line for vehicles, which includes assembly installations and an adjusting device for adjusting the axle geometry according to the present invention.
Typically, in conventional assembly plants, the axle geometry of a vehicle is manually adjusted after completion of the assembly process. At this point, the vehicle has left the area of the assembly installations and the vehicles are manually transported to an area, which includes, if necessary, several parallel stations for adjusting the axle geometry. These stations may have pits in which mechanics are working. The vehicles are placed over these pits. The chassis of the vehicles can then be adjusted by the personnel in a shop-like manner.
U.S. Pat. No. 5,040,303 discloses a method and a device for adjusting the axles of a vehicle. This device includes an automatic adjusting station that is arranged in a pit. To adjust the vehicle axles, the vehicle must be placed over the adjusting station, for instance by a person, and at least by means of the vehicle""s own chassis. The adjusting station is configured in such a way that adjustments are performed on vehicles that have a so-called xe2x80x9csetxe2x80x9d chassis. In these vehicles, at least the full vehicle weight has already acted on the chassis over a prolonged period of time, so that stresses of various kinds have already partly subsided.
U.S. Pat. No. 5,027,275 also discloses a method and a device for adjusting the axles of a vehicle. This device includes an automatic adjusting station that is arranged in a pit. To adjust the vehicle axles, the vehicle must be placed over the adjusting station, for instance by a person, and at least by means of the vehicle""s own chassis. Again, the adjusting station is configured in such a way that adjustments can be performed on vehicles that have a xe2x80x9csetxe2x80x9d chassis. In addition, a possible inclination of the steering wheel is detected by means of a steering wheel measuring balance and is taken into account in the axle adjustment.
German laid-open patent application DE 196 36 427 A1 discloses a method and a device for measuring and adjusting the axle geometry of a vehicle. This method assumes that the front and rear axles are pre-assembled in separate assembly areas. Simultaneously to the pre-assembly, the axle geometry is adjusted in that the positions of the axles are detected with respect to a relative coordinate system. This relative coordinate system is based on locking pins in the vehicle floor, for example. Subsequent positions of the wheels of the vehicle can be determined via the position of the brake disks in the relative coordinate system. The thus pre-assembled and adjusted axles are then mounted to the floor of the vehicle.
U.S. Pat. No. 5,731,870 discloses a method and a device for optically measuring the track and inclination values at the vehicle wheels. To this end, the vehicle is placed into a measuring station by means of its own chassis. Here, too, the adjusting station is configured in such a way that the adjustments are made on vehicles that have a xe2x80x9csetxe2x80x9d chassis.
Finally, Japanese Patent JP 10 15 76 53 discloses a method for adjusting the axle geometry of vehicles in a vehicle production plant. The axle geometry values of the vehicles are detected and adjusted downstream from the assembly installations where the vehicles are produced. Again, the vehicles are transported to the measuring and adjusting stations by means of their own chassis. Here, too, the adjusting station is configured in such a way that the adjustments are made on vehicles whose chassis have xe2x80x9csetxe2x80x9d.
It is one drawback of these prior art devices that each vehicle must he individually and manually transported to the test stands used for chassis adjustment, which is time consuming and costly. Particularly in the case of a production plant or assembly line for automotive vehicles, this impairs the rapid production flow in such a way that the chassis geometry has to be adjusted in so-called rework stations. These are workstations that are equipped and organized like shops, in which the newly produced vehicles must be manually adjusted outside the assembly installations, which are typically automated.
A further significant drawback is that the vehicles have already been set on their wheels prior to being transported to the measuring device. To reach an approximately stationary, i.e., a xe2x80x9csetxe2x80x9d state, a certain settling behavior has to be awaited first. During this process, all movable and spring-action components of a chassis settle while various stresses are reduced. This is no problem in vehicles that are already in use, since the settling of the chassis can be considered complete because of use. In contrast, after a new vehicle produced in an assembly plant is first set down, one has to wait for a certain settling behavior. This, too, can considerably interfere with the rapid and, in particular, fully automated production flow in an automotive assembly plant or assembly line.
It is one object of the invention to provide a method for efficiently measuring wheel alignment of a vehicle. Another object is to provide an improved method for adjusting the axle geometry of a vehicle. It is a further object of the present invention that this method be automatically performed, for example with the aid of robots, in particular in fully automated production plants. A further object of the invention is to provide an adjusting device that is suitable for performing these methods. It is another object of the invention to provide a production line or assembly line for vehicles, in which the assembly installations of the assembly line interact with the adjusting device according to the invention in a particularly advantageous manner.
According to one formulation of the invention, these and other objects are achieved by a method that includes suspending the vehicle; and, while the vehicle is suspended, measuring a wheel alignment parameter for a wheel of the vehicle. According to another formulation, the invention is directed to a method in which the vehicle is placed in an empty-weight position while still in a vehicle production line, following a chassis assembly stage for the vehicle. Then, while the vehicle is in the empty-weight position, an alignment parameter for a wheel of the vehicle is measured. The alignment parameter is then used to adjust an axle geometry for the vehicle. Thereafter, the vehicle is removed from the production line.
The method is particularly suitable for vehicles that have not yet been set down onto a lane after completion of the production process. The adjustment according to the invention is done automatically by taking into account at least the measurement values that are detected on the wheels mounted to the chassis of the suspended vehicle.
Parameters that characterize the axle geometry of a vehicle include, in particular, the track and the inclination, but also, preferably, the caster of the wheels of the vehicle. Therein, the wheels are rims that are fully equipped with tires.